The present invention relates generally to wireless electromechanical locks, and more particularly to batteryless timekeeping for wireless electromechanical locks.
Electromechanical locks use a combination of electronic and mechanical components, typically including an electronic controller, a mechanical locking mechanism, and an electronic actuator capable of switching mechanical components between locked and unlocked states. Mechanical locking mechanisms may comprise, for instance, mechanical bolts and strikes. Some electronic actuators entirely open and close locks, such as by shifting a bolt. Other electronic actuators only release pins or catches so that an operator may open the lock. In either case, electronic actuators are controlled by electronic controllers, which respond to user inputs such as RFID information, passkeys, or other digital certificates. Controllers process and authenticate user inputs, and command electronic actuators to open or close accordingly. Electromechanical locks are conventionally powered with batteries, or by wired connection to a power grid.
Some electromechanical locks incorporate timekeepers such as real time clocks, enabling authentication procedures to depend on time. Such a lock might be configured, for instance, to allow the bearer of a particular digital certificate access into a restricted area only at certain times of day, or on certain days of each month. It is essential for such purposes that the electromechanical lock controller be provided with a trusted time, and not rely on operator-supplied or otherwise unsecured time values for certification.
Some electromechanical locks utilize near field communication (NFC) to communicate wirelessly with an operator. An operator-side interface device can inductively power the electromechanical lock for the duration of certification, thus allowing the lock to dispense with batteries and wired grid connections, reducing maintenance requirements and simplifying installation. Because NFC locks only receive power during intermittent interaction with an operator-side NFC initiator, however, a conventional continuous timekeeper such as a continuously active real time clock cannot be used. As a result, the prior art does not support trusted timekeeping for batteryless locks.